Catalytic oxidation of organic compounds



Patented Dec. 30, 1930 UNITED STATES PATENT OFFICE ALFRED WOHL, OF DANZIG-LANGFUHR, FREE CITY OF DAN ZIG, ASSIGNOR TO I. G.

FAIRBENINDTUSTRIE AKTIENGESELLSCHAFT, OI FRANKFORT-ON-TEE-MAIN, GER- I MANY, A CORPORATION OF GERMANY CATALYTIC OXIDATION OF ORGANIC COMPOUNDS No Drawing. Original application flied. August 11, 1921, Serial No. 491,530, and in Germany June 22, 1916. Divided and this application filed August 8,, 1928. Serial No. 884,481.

I have found that the oxidation of hydrocarbons by means of free oxygen can be carried out with the production of valuable intermediary products if temperatures below red heat are employed and if catalysts are used that have no tendency for accumulating heat and splitting off hydrogen, as platinum metals commonly do, but which simply act as oxidizing agents owing to their containing oxygen in a loosely combined state. The catalysts must be non-volatile and capable of being regenerated under similar conditions of temperature by the introduced oxygen, and neither their higher nor their lower combinations with oxygen must be considerably vaporized at the said temperatures.

Vanadic oxides have proved very suitable for carrying out the reaction. They can be replaced by other similarly acting catalysts, or-mixtures with same. As instances of such catalysts may be mentioned molybdic oxide, uranic acid in the form of the yellow potassium uranate, and chromic acid as bichromate. In other words, such metallic oxygen compounds are suitable which-below red heat are converted into anhydrous acids or oxides of a non-basic nature, so that carbonyl comounds or acids are not absorbed which would liaad to a farther going combustion. The catalyst should be uniformly distributed on a suitable bed or support, for instance, pumice stone in as thin a layer as possible. With this object in view vanadic oxide is precipitated, for instance, from its colloidal solution by animal charcoal, or bichromate is finely powdered and either ofthe two compounds is shaken for some time with small pieces of pumice stone which has previously been soaked with gum solution and dried. The shaking is continued until the catalyst is uniformly distributed over the surface of the pumice stone or the like. In each particular case the most favorable conditions as to temperature, speed of air for a definite active layer, degree ofv moisture and percentage of oxygen in the gas to be used, concentration of the substance to be oxidized,

&c., must be ascertained. I can carry out my of-the catalyst and its regeneration may be performed alternately.

While the temperature should be below redheat, that is below about 580 0., in most cases much lower temperatures will be sufficient.

If heated atmospheric air ofabout 200 0. be-passed over fused anthracene and subsequently over the catalyst described at a temperature of about 250 0., the vapors of the anthracene going over will already contain some anthraquinone. If the catalyst be beated to about 400 0., pure anthraquinone is obtained, but the formation of carbon di oxide is increased. The same product is obtained by using triphenylmethane, whereas toluene yields benzaldehyde and benzoic acid. Tar fractions containing aromatic hydrocarbons with side-chains yield mixtures of aldehydes and acids, whilst high molecular unsaturated hydrocarbons contained. for instance, in brown-coal tar are converted into acids by this oxidation.

I have further found that instead of using as catalysts the oxides of non-basic character, such as oxides of vanadium or molybdemum and the like, I can profitably use the metal salts of acids derived from said elements, as silver vanadate, copper vanadatc and so on, for example salts of heavy metals with such acids, the elements of which form more than one degree of oxidation. By the application of such metal salts the temperature of reaction is greatly decreased. Apart from the temperature, the efficiency of the catalyst depends essentially upon the pressure of oxygen that controls the speed of the regeneration of the catalyst surface. It is obvious that low temperatures of reaction are favorable for the production of valuable products of oxidation.

As such salts which may be used as catalysts are to be mentioned: vanadates,chromates, molybdates, uranates, stannates, arsenates and the like of metals, such as copper, silver, lead, thallium, platinum, cerium, nickel, cobalt &c.

I have also found that I can carry out the process not only by passing the vapors of the substance to be oxidized together with the air or oxygen over the catalyst suitably distributed, but I can also treat the substance to be oxidized either in a liquid state or dissolved in a neutral solvent by heating it with the catalyst in the presence of oxygen or atmospheric air preferably under increased pressure and agitation. I

For example, sodium orthovanadate (prepared from 100 grams of vanadic oxide) is precipitated with the equivalent aihount of silver nitrate (560 grams). The reci itate after being'washed and filtered is istri uted, by strong shaking, onto 4 kilo rams of granulated pumice stone which as previously been soaked with 2 liters of a 5 per cent um solution and then dried. After eating or4 hours at 300 C. in a current of air, the catalyst is ready for use. In a current of oxygen, by which the catalyst is always regenerated, at a temperature of 280 C. nearly pure anthraquinone is obtained from anthracene without loss by combustion, if the current of oxygen is sufficiently quick and the concen- {ration of the anthracene correspondingly ow.

Another very active catalyst can be obtained according to the following method One molecular proportion ofvanadic oxide (V 0 is dissolved by means of 6 molecular proportionsof caustic alkali and precipitated with a solution of 3 molecular proportions of copper sulphate. The enish yellow precipitate, after being was ed and sucked off, is then suitably distributed onto pumice stone (about 50 times the quantity of the vanadic oxide used) which has beforehand been soaked with gum solution by strongly shaking, and moderately heated in a current of oxygen until the organic substance has disappeared. The catalyst thus prepared converts at 180 to 190 C. anthra- I cene into anthraquinone without any loss. The regeneration of the catalyst is, however, rather slow under these circumstanoesand increases with the temperature and the oxygen pressure. It is therefore increased, when the oxygen is passed in a cycle under increased pressure and while replacing the oxygen consumed, so that the places where the anthraquinone is vaporized, the catalysts space and the place where the anthraquinone is deposited, are passed in regular turn.

This application is a division of my copending application for patent, Ser. No. 491,530, filed August 11, 1921.

What I claim' is:

which comprises subjecting anthracene in the vapor phase to oxidation by oxygen in the presence of an oxide of vanadium as'a catalyzer. at a temperature of about 300 C. to 500C."

2. The method of oxidizing. anthracene, which comprises passing. a mixture of an- 1. The method of oxidizing anthracene, 

